Other mistake: The radio station had no power or telephone lines anywhere in the vicinity, and the lines would not have been buried in 1937. A telephone is seen on the wall inside the building, yet it couldn't have been connected to anything. There wasn't a generator to power the radio transmitter, because it would have had an exhaust pipe through the roof, nor was there any adjacent building to house a generator.
O Brother, Where Art Thou? (2000)
1 other mistake
Directed by: Joel Coen, Ethan Coen
Starring: John Goodman, George Clooney, John Turturro, Holly Hunter, Tim Blake Nelson
Factual error: When the "Little Wharvey Gals" are singing they show a shot of the crowd in which there is a man smoking a filtered cigarette. Cigarettes were not filtered until the late '40's.
Ulysses Everett McGill: I don't get it, Big Dan.
More trivia for O Brother, Where Art Thou?
Question: In the KKK scene, Homer Stokes says "The color guard is colored." Did he mean this literally, like Everett was a black man, or did he mean that he was white (unlikely because John Goodman is white and so is he), or is he mistaking Everett for a black man because of his dirty face?
Answer: He mistook Everett for a black man because of his dirty face. It's the only way the line makes sense.
J I Cohen